Up to now, all amendments have been proposed and implemented as codicils appended to the main body of the Constitution. If at least two-thirds of the legislatures of the states so request, Congress is required to call a convention for the purpose of proposing amendments. This provision, many scholars argue, checks the power of the Congress to limit potential constitutional amendments.
1 The pulmonary veins carry oxygenated blood from the lungs into the left atrium where it is returned to systemic circulation.  The aorta is the largest artery in the body. It carries oxygenated blood from the left ventricle of the heart into systemic circulation.
The arch of the aorta is the second major anatomical region of the aorta; it curves above the heart between the ascending and descending aorta. All of the blood delivered from the heart to the systemic tissues of the body passes through the aorta, making it the largest artery in the human body.